Foundation: build CoreFoundation as /MD
Foundation: build CoreFoundation as /MD

Use /MD and /MDd mode compilation rather than /MT or /MTd as per
Microsoft's recommendation.  This allows us to use a shared C runtime.
The static MSVCRT/ucrt cannot be intermingled with a dynamic one.

apple/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation,apple/swift-corelibs-foundation,parkera/swift-corelibs-foundation,apple/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation,e78l/swift-corelibs-foundation,apple/swift-corelibs-foundation,parkera/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation